We investigate optical absorption and emission spectra of Sm3+ ions in Sm(DBM)3Phen-doped polymethyl methacrylate (PMMA). Based on the Judd-Ofelt theory, the optical intensity parameters are calculated to be Ω2 = 13.76 × 10-20cm2, Ω4 = 3.41 × 10-20 cm2, Ω6 = 4.01 × 10-20 cm2 from the absorption spectrum of Sm(DBM)3Phen-doped polymethyl methacrylate. The optical intensity parameters have been used to calculate the total radiative transition rate (676.5 7 s- 1 ) and radiative lifetime (14 78μs) of the 4G5/2 exciting state. The stimulated emission cross-sections σij and the fluorescence branch ratios for the 4G5/2 → 6FJ and 4G5/2 → 6HJ ransitions are also evaluated. The analysis reveals that Sm(DBM)3Phen-doped PMMA is promising for applications in rare-earth-doped polymer devices.